Cross-Reference to Related Applications
This patent application is related to the following copending applications assigned to the common assignee hereof:
U.S. Ser. No. 586,086, filed Mar. 5, 1984, entitled "Independent Wheel Suspension System Using Thrust Bearing Constant Velocity Universal Drive Joints As Suspension Members";
U.S. Ser. No. 586,012, filed Mar. 5, 1984, entitled "Independent Wheel Suspension System Using Thrust Bearing Constant Velocity Universal Drive Joints, Bending and Torsional Motion Resistance Suspension Members And A Transversely Pivotable Differential";
U.S. Ser. No. 586,056, filed Mar. 5, 1984 entitled "Independent Wheel Suspension System Using Thrust Bearing Constant Velocity Universal Drive Joints As Suspension Members In Combination With A Single Prop Shaft Joint and A Transversely Pivotable Differential";
U.S. Ser. No. 586,022, filed Mar. 5, 1984 entitled "Independent Wheel Suspension System Using Constant Velocity Universal Joints In Combination With A Single Prop Shaft Joint And Mounted Differentials"; and
U.S. Ser. No. 586,098, filed Mar. 5, 1984 entitled "Independent Wheel Suspension Using Thrust Bearing Constant Velocity Universal Drive Joints As Suspension Members in Combination With A Wheel Assembly And Differential Coupled To Pivot About A Transverse Stabilizer"; and
U.S. Ser. No. 586,054, filed Mar. 5, 1984 entitled "Independent Wheel Suspension System Having A Differential Pivotable About Two Axes".
1. Field of the Invention
The present invention pertains to independent wheel suspension systems and, more particularly, to independent wheel suspension systems wherein constant velocity joints are used as a wheel suspension member to carry thrust loads.
2. Description of the Prior Art
The present invention has particular application to both front and rear wheel independent suspension systems wherein universal joints are used to transfer power from a power delivery unit, normally including an engine, transmission, and a differential housing, through half-shaft drive axles to the driving wheels. As a vehicle moves along a road surface, the wheels naturally experience an up and down movement relative to the driving surface. This movement is referred to as jounce and rebound, and the road clearance of various vehicle components vary accordingly. If the wheels are allowed to move in a plane approximately normal to the driving surface, such up and down movements have heretofore required corresponding changes in the swing length between the wheel and the differential of the power delivery unit. Such changes in swing length are normally effected by allowing an axial adjustment either of a driving member relative to the wheels or of one member of a driving member relative to another. Because of the dynamic loads associated with these up and down movements of the wheel and the geometric movements of the suspension members as a result of the various load and road conditions experienced by the wheels of a vehicle, past suspension system design efforts have taken the approach of completely isolating the drive system components from the suspension system components to prevent the application of suspension loads to the power delivery unit or torque translating drive components of a vehicle. As a result of this approach the structural design criteria of prior art vehicles is to limit the torque translating components of a vehicle to carry only torque loads to propel the vehicle and to design a separate suspension system to carry the loads associated with the up and down movement of the vehicle wheels as a result of load and/or road variations.
Independent wheel suspension systems generally contemplate the use of two general types of universal driving joints: the Cardan-type joint and the constant velocity type joint. The Cardan-type joint consists of two yokes connected by a plain or rolling type bearing on the ends of a Cardan or cruciform-shaped cross. The cross consists of a block and two pins, one pin being smaller than the other and passing through it. Even though heat-treated alloy steels are used throughout, the small pin diameters limit the capacity of the joint to carry axial thrust loads, such axial thrust loads normally impose stresses on the pins which are multiples of the stresses associated with carrying normal driving torque. Moreover, the stresses augment each other deleteriously, through vector addition. But the major deterrent to using a single Cardan-type joint in an independent rear suspension system is the severe limitation on the allowable angle of articulation under high torque loads. This is because the velocity ratio of the speed of the driving to the driven shaft pulsates or "knuckles" with increasing amplitudes as the angular articulation between these shafts increases. The cyclic speed pulsations significantly increase as articulation between the driving and driven joint members increase. Such speed pulsations cause correspondingly higher dynamic stresses on the Cardan cross pins and corresponding vehicle vibration and noise as loads of any appreciable inertia are translated through the joint. The higher dynamic stresses wear the joint structure to degeneratively further increase the speed variations and further limit the ability of the Cardan joint to carry high torque loads. Moreover, under thrust loads, the normal manufacturing tolerance of a Hooke's joint or Cardan joint, by themselves, cause unacceptable vibrations.
To avoid the foregoing deleterious stress and load carrying consequences of Cardan-type universal joints, their use in vehicles is generally limited to applications where the normal angular articulation between the driving and driven members is substantially less than ten degrees, usually less than three degrees.
Constant velocity universal joints have heretofore been used with independent wheel suspension systems to avoid the debilitating effects of the foregoing cyclic speed variations of Cardan-type joints while permitting substantially greater articulation angles of the wheel with respect to the drive shaft or the drive shaft with respect to the differential of the power delivery unit. Constant velocity universal joints of the type that provide uniform velocity between the driving and driven members at any intersecting angle of the joint are shown in U.S. Pat. No. 2,046,584 to Rzeppa, U.S. Pat. No. 3,162,026 to Ritsema, and also commonly assigned U.S. Pat. Nos. 3,688,521, 3,928,985, 4,240,680 and 4,231,233, the specifications of which are hereby incorporated by reference. Such known constant velocity universal joints have heretofore been used to carry the driving torque transmitted through the spherical ball members of the joint. These balls ride in sets of opposing axial grooves formed on a partially-spherical inner joint member and on a partially-spherical outer joint member. A ball guide cage is positioned to capture and guide the balls through a homokinetic plane or rotation wherein the centers of the balls very nearly bisect the articulation angle between the driving and driven shafts resulting in a constant velocity transmission of rotary motion. The ball cage normally consists of upper and lower partially-spherical surfaces guided, respectively, on the partially-spherical inner and outer surfaces of the joint members but are designed to have radial clearances therebetween in order to insure lubrication of the surfaces and thereby avoid excessive heat build up.
In any event, the balls and axial grooves of the constant velocity universal joint have heretofore been used to translate the driving torque while the spherical portions of the inner and outer joint members experience the internally generated loads, such internally generated loads being carried either by direct contact between the inner and outer joint members or through the interposed spherical surfaces of the cage. As taught in U.S. Pat. No. 3,789,626, to Girguis, where one constant velocity universal joint was used as a fixed joint, as in the drive shaft of a rear drive motor vehicle, an object of such an application is to maintain the joint elements free of axial internal forces, even though the joint was constructed to absorb forces, at least those related to torque translation. In fact, the joint was designed to avoid transmitting axial forces through the control element. Therefore, when used at opposite ends of a driving half-shaft, one of such constant velocity universal joints has heretofore been of the axial slip or plunging variety, allowing axial movement of the driven joint with respect to the driving joint, and the constant velocity universal joint at the other end has been of the non-axial slip or fixed type not permitting such axial movement.
It is also known that, to obtain proper steering characteristics, the camber of the wheel, or the angle that a longitudinal plane therethrough makes with the axis, as viewed from the front or rear of the vehicle, must be maintained within predetermined limits in order to afford the desired handling and steering characteristics. However, as the independent wheel suspension causes the wheel to move about a swing axis having a pivot at the side of the differential, the wheel camber changes by an amount varying with the swinging movement of the wheel. To minimize the resulting change of camber, various structures have heretofore been provided to lengthen the effective swing radius of the wheel. However, such extra structures have been comparatively complex and costly.